Generation of Uniform Magnetic Field between Face-to-Face HTS Bulk Magnets

Abstract

Aiming to develop the compact nuclear magnetic resonance devices, the authors have been developing the uniform magnetic fields in the space between the face-to-face magnetic poles which contain HTS bulk magnets. The authors deformed the original convex shape of the magnetic field distribution to concave by attaching a ferromagnetic iron plate of 20 mm and 100 mm in diameter on one of the pole surfaces. The magnetic field distribution precisely measured along x-axis changed from concave to convex with increasing distance from the magnetic pole surface, which suggested the presence of magnetically flat region. From the results of mapping on the field uniformity data, we have succeeded in obtaining the field uniformity under 500ppm in the space of 4 x 4 x 0.8 mm3 when the magnetic poles emitting concave and convex field distributions were settled face-to-face with various gaps 30-70 mm. This performance exceeded the target value of 1,500ppm which is necessary to detect the NMR signals.

Formation of uniform magnetic flux distribution for NMR magnets using HTS bulk magnets activated by pulsed-field magnetization

“…The distance between face-to-face poles was set to 30 mm. As reported in [13], the best uniformity of 463 ppm was obtained at 1.25 T over a wide area of less than 1,500 ppm at the center portion of the pole, which is thinly painted by colors in the figure. The area whose uniformity was less than 1,500 ppm was estimated to be 23 mm 2 .…”

“…Hence, a uniform space of 4×4×1.1 mm 3 will be available to detect its NMR signal for the sample with dimensions of 4×4×0.5 mm 3 . The performance was improved compared with that shown in [13].…”